fix(audit): low-tail cleanup — session/logout/unread/presence/forward

Clears the clean 🟡 remainders from the feature audit (gate-green, 677 tests):
- F3: getFallbackSession prefers the session-blob/legacy source with the later
  expiresAt (a downgrade→upgrade could boot on a stale blob's dead token).
- F6: server-forced logout (SessionLoggedOut) now mirrors logoutClient —
  pushSessionToSW() + best-effort revokeOidcTokens for OIDC sessions (the search
  plaintext wipe was already added).
- N5: deleteUnreadInfo parent fallback `?? roomId` → `?? []` (latently spread the
  roomId string into chars).
- P10: useUserPresence re-seeds when the User object appears after first render.
- forward: strip m.mentions so forwarding doesn't re-ping the original mentions.

Left open: F5 (OIDC expiry not reachable in persistTokens), N6/H10/D7 (minor /
runtime-verify). See LOTUS_TODO.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/room/message/forwardContent.ts

@@ -29,6 +29,9 @@ export function buildForwardContent(
   }
 
   delete content['m.relates_to'];
+  // Drop intentional mentions so forwarding a message doesn't re-ping the
+  // originally-mentioned users (they're not in the destination room's context).
+  delete content['m.mentions'];
   if (typeof content.body === 'string') {
     content.body = trimReplyFromBody(content.body);
   }

src/app/hooks/useUserPresence.ts

@@ -29,6 +29,10 @@ export const useUserPresence = (userId: string): UserPresence | undefined => {
   const [presence, setPresence] = useState(() => (user ? getUserPresence(user) : undefined));
 
   useEffect(() => {
+    // Re-seed when the User object appears/changes after first render — the
+    // useState initializer only ran if `user` already existed at mount, so a
+    // late-arriving user would otherwise show no presence until the next event.
+    if (user) setPresence(getUserPresence(user));
     // Subscribe on mx (MatrixClient) rather than on individual User objects.
     // User objects have a default 10-listener limit; the same user can appear
     // in many components simultaneously (avatars, member list, etc.) and

src/app/pages/client/ClientRoot.tsx

@@ -44,6 +44,8 @@ import { stopPropagation } from '../../utils/keyboard';
 import { SyncStatus } from './SyncStatus';
 import { AuthMetadataProvider } from '../../hooks/useAuthMetadata';
 import { getFallbackSession, removeFallbackSession } from '../../state/sessions';
+import { pushSessionToSW } from '../../../sw-session';
+import { revokeOidcTokens } from '../../../client/oidcLogout';
 import { useSessionSync } from '../../hooks/useSessionSync';
 import { installCryptoDiagLog } from '../../utils/cryptoDiagLog';
 import { AutoDiscovery } from './AutoDiscovery';
@@ -143,7 +145,17 @@ function ClientRootOptions({ mx }: { mx?: MatrixClient }) {
 const useLogoutListener = (mx?: MatrixClient) => {
   useEffect(() => {
     const handleLogout: HttpApiEventHandlerMap[HttpApiEvent.SessionLoggedOut] = async () => {
+      // Clear the SW's cached bearer token so it stops attaching the now-revoked
+      // token to media fetches (mirrors the manual logoutClient path).
+      pushSessionToSW();
       mx?.stopClient();
+      // Best-effort issuer revocation for OIDC sessions (the token is already
+      // server-revoked here, but revoke the refresh token too). Before we drop
+      // the stored session below.
+      const loggedOutSession = getFallbackSession();
+      if (loggedOutSession?.oidc) {
+        await revokeOidcTokens(loggedOutSession).catch(() => undefined);
+      }
       await mx?.clearStores();
       // The opt-in local search index holds DECRYPTED message plaintext. Wipe it
       // on server-forced logout too (token expiry / remote sign-out / password

src/app/state/room/roomToUnread.ts

@@ -83,7 +83,9 @@ const deleteUnreadInfo = (roomToUnread: RoomToUnread, allParents: Set<string>, r
   allParents.forEach((parentId) => {
     const oldParentUnread = roomToUnread.get(parentId);
     if (!oldParentUnread) return;
-    const newFrom = new Set([...(oldParentUnread.from ?? roomId)]);
+    // `from` is always a Set for parent aggregates; the fallback must be an
+    // iterable of ids, NOT the roomId string (which would spread into chars).
+    const newFrom = new Set([...(oldParentUnread.from ?? [])]);
     newFrom.delete(roomId);
     if (newFrom.size === 0) {
       roomToUnread.delete(parentId);

src/app/state/sessions.ts

@@ -264,7 +264,21 @@ export const removeFallbackSession = () => {
 // the next setFallbackSession then persists the blob. When both exist the blob
 // wins by construction.
 export const getFallbackSession = (): Session | undefined => {
-  const persisted = readSessionBlob() ?? readLegacyKeys();
+  const blob = readSessionBlob();
+  const legacy = readLegacyKeys();
+  // Prefer the atomic blob, EXCEPT when the legacy keys carry a later expiry: a
+  // pre-blob build's token refresh writes only the legacy keys, so a
+  // downgrade→upgrade can leave a stale blob newer than fresh legacy keys →
+  // booting on a dead token. Whichever has the later expiresAt wins.
+  let persisted = blob ?? legacy;
+  if (
+    blob &&
+    legacy &&
+    typeof legacy.expiresAt === 'number' &&
+    (typeof blob.expiresAt !== 'number' || legacy.expiresAt > blob.expiresAt)
+  ) {
+    persisted = legacy;
+  }
   if (!persisted) return undefined;
   return sessionFromPersisted(persisted);
 };